Internal combustion engine connecting rod

ABSTRACT

An internal combustion engine connecting rod capable of preventing rotation or relative slippage of a slide metal piece even if the nail of the slide metal piece is not abutted. An internal combustion engine connecting rod comprising a hole in the end of the connecting rod main body, the end being divided into a plurality of parts circumferentially of the hole, and a slide metal piece ( 10 ) disposed on the inner peripheral surface of the hole, wherein the inner peripheral surface of the hole is provided with slits (L, L′) extending in one direction at an angle of 13-90° with respect to the circumferential direction.

TECHNICAL FIELD

The present invention relates to an internal combustion engineconnecting rod whose end is divided and disposed circumferentially withrespect to a hole formed therein, and which has a slide metal piecemounted in the hole. More particularly, the invention relates to atechnique for preventing relative rotation of the slide metal piece withrespect to the hole.

BACKGROUND ART

FIG. 10A is a perspective view showing a large end of the main body ofthe internal combustion engine connecting rod (referred to simply as“connecting rod” hereinafter) having the structure described above. Ahole 2 is formed in the center of the large end 1. The large end 1 isdivided into a rod portion 3 and a cap portion 4 which are disposed astwo semi-circles in the longitudinal direction of the hole 2, and therod portion 3 and the cap portion 4 are mounted with bolts which are notshown in the drawing. At an inner periphery of one mating surfacevicinity of the rod portion 3 and the cap portion 4, as shown in anenlarged view in FIG. 10B, grooves 5 which are in the circumferentialdirection and which gradually deepen until the mating surface isreached, are formed so as to be on different sides from each other, andsuch that the mating surface is disposed therebetween. The slide metalpiece 10 shown in FIG. 11 is mounted in the hole 2 of the connecting rodbody having the structure described above.

As shown in FIG. 11A, the slide metal piece 10 comprises two ring halves10 a and 10 b obtained by dividing the ring. At one mating portion ofthe ring halves 10 a and 10 b, nails 11 which extend from the outerperiphery side are formed so as to be opposite to each other. The slidemetal piece 10 is fit into the hole 2 by the nails 11 being accommodatedin the grooves 5 of the connecting rods, and the slide metal piece ismounted into the hole 2 with a fixed tightness by tightening the bolts.Furthermore, relative movement of the slide metal piece 10 is preventedby the end surfaces of the nails 11 which are accommodated in thegrooves 5, being caused to abut the end surface of the rod portion 3 orthe cap portion 4.

In this invention, the rod portion 3 and the cap portion 4 are formedseparately by sintering, forging, casting or the like, but they may alsobe formed integrally. In the case where the rod portion 3 and the capportion 4 are formed integrally, the connecting rod may be formed first,and then the hole and the grooves are mechanically machined. The rodportion and the cap portion are then divided by being split so as tobreak, and thus have a similar structure to that described above, andthen the slide metal piece is mounted. In this case, the machining ofgrooves like those shown in FIG. 10B is difficult. As a result, as shownby the broken lines in the same drawing, the connecting rod is machinedto form grooves which straddle the rod portion 3 and the cap portion 4.Furthermore, for both the embodiment having the rod portion 3 and thecap portion 4 formed separately, and for that having the integralstructure, which was divided by being mechanically machined and thencarrying out a breaking-split, the slide metal piece may be mountedwithout providing grooves for fixing the slide metal piece.

FIG. 12A is a cross sectional view showing the breaking-split typeconnecting rod described above in a state in which the crank pin 15 ismounted. Because the nail 11 of the slide metal piece 10 does not abutthe end surface inside the groove 5, as shown in FIG. 12B, the slidemetal piece 10 may rotate due to deformation of the large end 1 causedby load being exerted on the connecting rod. In addition, by beingdeformed from the unloaded state in FIG. 13A, to the state in FIG. 13Bin which the large end was deformed in the longitudinal directionthereof, as shown in FIG. 13C, the nail 11 is pressed in the directionof the arrow and there is a danger that the base plate B will eventuallybreaking due to fatigue. Also, broken pieces from the nail 11 may becomecaught between the crank pin 15 and the slide metal piece 10, and in theworst case, the slide metal piece 10 and the crank pin 15 may heat up.

In addition, as shown in FIG. 14A, a slide metal piece 10 having no nailmay also be used. In this case, it is easier for the large end to deformdue to load applied to the connecting rod than in the case describedabove in which the slide metal piece is provided with nails. As shown inFIG. 14A, crush relief portions 20 are formed at both ends of the ringhalves 10 a and 10 b which comprise the slide metal piece 10. The crushrelief portion 20 is formed such that its thickness decreases as the endthereof is approached, by causing the diameter of the inner peripheralsurface to gradually increase as the end is approached. As shown in FIG.14B, in the connecting rod in which the rod portion 3 and the capportion 4 are separately formed, when these two portions are mounted,the joint surface may be slid. In this case, the crush relief portions20 prevent localized contact between the slide metal piece 10 and thecrank pin 15.

Furthermore, if the crush height (the height of the slide metal piecewhich projects from the hole in the large end in an unloaded state) isexcessive, due to the elastic deformation of the mating portion of thering halves 10 a and 10 b, the crush height portion distends toward theinner side, and the effective inner diameter of the shaft receivingmetal piece is decreased. In that case also, the crush relief portion 20functions to prevent localized contact between the slide metal piece 10and the crank pin 15.

However, when the slide metal piece 10 rotates for the above describedreason, the crush relief portion 20 is not able to function to preventthe localized contact between the slide metal piece 10 and the crank pin15. That is to say, the crush relief portion 20 functions to preventlocalized contact between the slide metal piece 10 and the crank pin 15along the direction of the joint surface of the rod portion 3 and thecap portion 4. Accordingly, when as shown in FIG. 14C, the slide metalpiece 10 rotates and the phase is slid, the portion which is slid anddistends towards the inner side becomes close to the crank pin 15 side,and thus there is localized contact between the sliding portion and thecrank pin 15. Furthermore, when the large end 1 in an unloaded stateshown in FIG. 13A is deformed in the longitudinal direction so as to bein the state shown in the FIG. 13B, localized contact is more intense,and this may cause great damage to the inner peripheral surface of theslide metal piece 10.

Furthermore, this problem is common to all configurations of the slidemetal piece, and due to deformation and the like of the large end causedby load being applied to the connecting rod, relative micro slippage ofthe slide metal piece and the hole in the large end with respect to eachother is caused. Thus, fretting is generated when the outer peripheralsurface of the slide metal piece and the inner peripheral surface of thehole contact. That is to say, when the large end 1 deforms in thelongitudinal direction as shown in FIG. 13B, because the deformation ofthe hole 2 of the large end 1 of the slide metal piece 10 is not inexactly the same manner, relative micro slippage of the slide metalpiece 10 and the hole 2 with respect to each other is caused. Inaddition wear dust, generated due to fretting, accumulates between theslide metal piece 10 and the crank pin 15, and this damages the slidesurface. Also, minute cracks caused by fretting at the inner surface ofthe hole 2 develop, and in the worst case, there is the danger that theconnecting rod will be damaged.

Thus, an object of the present invention is to provide a connecting rodin which rotation and relative slippage of the slide metal piece isrestricted, and the problems described above are eliminated.

DISCLOSURE OF THE INVENTION

The present invention is a connecting rod comprising a hole in the endof the connecting rod main body, the end being divided into a pluralityof parts which are in a circumferential direction with respect to thehole and a slide member is disposed on the inner peripheral surface ofthe hole, wherein the inner peripheral surface of the hole is providedwith slits which extend in one direction at an angle of 13 to 90° withrespect to the circumferential direction.

In the connecting rod having the above described structure, slits areprovided at a predetermined angle in a circumferential direction withrespect to the inner peripheral surface of an end of the connecting rodmain body. As a result, frictional resistance of the slide member isincreased due to the unevenness of the slits, and relative rotation ofthe slide member is restricted. The slits may be formed by a polishingprocess such honing, grinding with a grindstone, or by carrying outshaving using a bite, or with a rotating tool such as a drill, a reamer,an end mill or the like. Furthermore, by adjusting the conveying speedand the rotation speed of the tool when the process is being carriedout, the angle of the slits with respect to the circumferentialdirection of the hole can be set at 13 to 90°. It is to be noted thatfor making the angle of the slits 90°, broaching, for example, may becarried out. However, in the case of the rotation processing, ifconsideration is given to processability, it is preferable that the slitangle does not exceed 35°.

When the slits are to be formed, by passing the tool through the hole inone direction thereof one time, or alternatively a number of times,slits can be formed which extend in one direction (linear slitting). Inthe present invention, the tool such as the grindstone, the bite and thelike, may also be inserted from the direction opposite to the directionreferred to above to form slits which cross the slits which were firstformed (cross slitting). That is to say, the present invention is aconnecting rod comprising a hole in the end of the connecting rod mainbody, the end being divided into a plurality of parts which are in acircumferential direction with respect to the hole and a slide member isdisposed on the inner peripheral surface of the hole, wherein the innerperipheral surface of the hole is provided with slits which extend inone direction at an angle of 17 to 90° with respect to thecircumferential direction and also with slits that extend in a directionwhich crosses the one direction. It is to be noted that, in the case ofcross slitting, the slits will form a net meshing and thus there is somereduction in frictional resistance. For this reason, it is necessary toset the angle so as to be larger in the case of cross slitting than inthe case of linear slitting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show the inner peripheral surface of the slide metalpiece of an embodiment of the present invention.

FIG. 2 is perspective view of a slide metal piece formed in the exampleof the present invention.

FIG. 3A is side view showing a state in which the slide metal piece ismounted in the rod portion and the cap portion, and FIG. 3B shows astate in which the rod portion and the cap portion are bolted.

FIG. 4 is a diagram showing the relationship between the angle of theslits in the circumferential direction and the metal piece slip torque.

FIG. 5 is a diagram showing the relationship between the tightness ofthe slide metal piece and the metal piece slip torque.

FIG. 6 is a diagram showing the relationship between the surfaceroughness of the inner peripheral surface of the large end and the metalpiece slip torque.

FIG. 7 is a diagram showing the relationship between the inner diameterof the large end and the slit angle, and the metal piece slip torque.

FIG. 8 is a side view of a connecting rod for showing a method formeasuring the relative slippage amount of the slide metal piece.

FIG. 9 is a diagram showing the relative slippage amount at respectiveangle positions of the slide metal piece.

FIG. 10A is a perspective view of the large end, and FIG. 10B is agreatly enlarged view of the portion indicated with the arrow B in FIG.10A.

FIG. 11A is a side view of the slide metal piece, and FIG. 11B is agreatly enlarged view of the portion indicated by the arrow B in FIG.11A.

FIG. 12A is a side view of the connecting rod, and FIG. 12B is a sideview showing the state in which the slide metal piece has been rotatedfrom the state shown in FIG. 12A.

FIG. 13A is side view showing the connecting rod, FIG. 13B shows thestate in which the connecting rod shown in FIG. 13A has been deformed inthe longitudinal direction thereof, and FIG. 13C is a perspective viewfor describing the load received by the nail of the slide metal piece.

FIG. 14A a side view of the slide metal piece for explaining crushrelief, FIG. 14B is a side view showing the connecting rod which is slidat the joint surface, and FIG. 14C is a side view of the connecting rodwhose slide metal piece has been rotated.

BEST MODE FOR CARRYING OUT THE INVENTION

The following is a description of an embodiment of the present inventionreferring to FIG. 1. FIG. 1A is an unfolded plane view of the innerperipheral surface of the hole 2 formed in the large end of theconnecting rod. The transverse direction in these figures is thecircumferential direction. On the inner peripheral surface of the hole2, slits L are formed by linear slitting, at an angle θ in thecircumferential direction. The slits L are lines of unevenness caused byusing a tool such as a honing grindstone for example, to mechanicallyprocess the material surface. The angle θ of the slits L in thecircumferential direction is set at 13 to 90° by the adjustment of therotation speed and the conveying speed of the tool.

FIG. 1B shows the hole 2 having slits L formed, wherein slitting iscarried out by a tool being conveyed in the direction opposite to thatin which it was conveyed in FIG. 1A, thus forming slits L′ which crossthe slits L. In this case in which cross slitting is carried out, theangle of the slits L and L′ is set at 17 to 90°. Also, by disposing aslide metal piece (slide member) in the hole 2 which has been providedwith the slits L and L′, the connecting rod is formed. In this case, theslide member is preferably mounted in the hole such that the tightnessof the slide member which is defined by the difference between the outerperipheral length thereof and the inner peripheral length of the hole,is made to be 0.05 mm or greater.

The slide metal piece is generally mounted on the large end, but thepresent invention may be applied by disposing the slide metal piece atonly the small end, or at both the large end and the small end.Furthermore, in the present invention, in the case where the nail of theslide metal piece does not abut an end surface of the rod portion or thelike, the effect of the nail is fully exhibited. However, the structurein which the nail of the slide metal piece abuts the rod portion and thelike (see FIG. 10A) may also be applied. In that case, the relativeslippage of the slide metal piece with respect to the hole at the timewhen the large end is deformed due to the load exerted on the connectingrod decreases, and thus the generation of fretting can be controlled.

EXAMPLES

Next, the present invention will be described in further detail usingconcrete examples. FIG. 2 is a perspective view of the slide metal piece(slide member) 10 of the example, which is formed for measuring sliptorque of the slide metal piece with respect to the hole of the largeend. The ring slide metal piece of the example is formed in the samemanner as the actual slide metal piece, except that a notch 10 c forengagement with the torque meter jig is formed at the end of the ringhalves 10 a and 10 b. As the slide metal piece 10, an SP material whoseouter peripheral surface was plated with Ni, whose inner peripheralsurface was plated with Pb—Sn—Cu and whose entire surface wassubsequently flush plated with Sn was used.

FIG. 3 shows the steps for mounting the slide metal piece 10 in thelarge end 1 of the connecting rod. The outer diameter of the slide metalpiece 10 is set so as to be larger than the inner diameter of the hole 2of the large end 1. As a result, as shown in FIG. 3A in which no load isapplied, the large end 1 protrudes by the amount of the crush height.When the bolts 18 are tightened in this state, the slide metal piece 10elastically deforms as shown in FIG. 3B and the large end 1 is in thehole 2 in a state in which it is pressure-inserted. Also, the tightnessis a value obtained by subtracting the inner peripheral length of thehole 2 from the outer peripheral length of the slide metal piece 10. Theconnecting rod main body portion is one formed by forging an FC-0205sintered member and dividing the large end 1 so as to be split in thelongitudinal direction thereof.

The tightness of the slide metal piece 10 was set to 0.1 mm and thesurface roughness (Ry) of the hole 2 of the large end 1 was set to 2 to3 μm. The angle of the slits in the circumferential direction was thenchanged and the slip torque was measured. The results are shown in FIG.4. It is to be noted that in the state of FIG. 3B, the torque meter jigis engaged with the notch 10 c of the slide metal piece 10, and torqueis applied to the jig. The torque when the slide metal piece 10 rotatesrelative to the hole 2 is referred to as the slip torque. As shown inFIG. 4 when the slit angle is varied between 5° and 30°, the slip torqueincreases as the slit angle increases. Furthermore, it can be seen thatin the case of linear slitting, when the slit angle is no less than 13°,the slip torque is 15 kgf·m, and in the case of cross slitting, when theslit angle is no less than 17°, the slip torque is 15 kgf·m.

Next, the surface roughness (Ry) of the hole 2 of the large end 1 wasset to 2 to 3 μm and the slit angle was set to be 15° and 30°. Thetightness of the slide metal piece 10 was varied and the slip torque wasmeasured. The results are shown in FIG. 5. As can be seen from FIG. 5,even when the tightness of the slide metal piece was the same, the sliptorque was changed by the slit angle. That is to say, in the case wherethe slit angle is 30°, in the case of both linear slitting and crossslitting, as long as the tightness is no less than 0.05 mm, the sliptorque will be not be less than 15 kgf·m. Also, in the case where theslit angle was 15° and the slitting was linear, if the tightness is noless than 0.07 mm, the slip torque will be no be less than 15 kgf·m.

Next, the tightness of the slide metal piece 10 was set to be 0.1 mm andalso the slit angle was set to 15°. The surface roughness (Ry) of theinner peripheral portion of the hole 2 of the large end 1 was changedand the slip torque was measured. The results are shown in FIG. 6. Asshown in FIG. 6, as the surface roughness increases, there is a tendencyfor the slip torque to increase, but it can be seen that the effect ofsurface roughness is limited. Thus, a surface roughness of the innerperipheral portion of the hole 2 of 2 μm can be considered to besufficient.

Next, the tightness of the slide metal piece 10 was set to 0.1 mm, thesurface roughness (Ry) of the hole 2 of the large end 1 was set to 2 to3 μm, and various slit angles were set and cross slitting was carriedout. The inner diameter of the hole 2 of the large end 1 was changed andthe slit torque was measured. The slide metal piece used for measuringwas formed in the same manner as that shown in FIG. 11, and theconnecting rod was formed with this slide metal piece. The actualtesting was then carried out. These results are shown in FIG. 7. As canbe seen from FIG. 7, the internal diameter of the hole 2 has no effecton the slip torque. Furthermore, it was confirmed that as long as theslip torque is no less than 15 kgf·m, the slide metal piece was not slidin the actual test.

The above results confirm that in the case of linear slitting, when theslit angle is set to be 13 to 90°, and in the case of cross slitting,when the slit angle is set to be 17 to 90°, slippage of the slide metalpiece is not caused. Furthermore, the tightness of the slide metal pieceis to be appropriately set in accordance with the slit angle such thatthe slip torque is greater than or equal to 15 kgf·m. For example, inthe case where the slit angle is 30°, it is sufficient for the tightnessof the slide metal piece to be 0.05 mm or more, and in the case wherethe slit angle is 15° and slitting is linear, the tightness should be0.07 mm or more. Furthermore, as shown from the results of FIG. 4 in thecase of linear slitting when the slit angle is 13°, and in the case ofcross slitting when the slit angle is 17°, it is sufficient for theslide metal piece tightness 0.1 mm or more. From the above, the rangefor the tightness of the slide metal piece is preferably to 0.05 mm orgreater, more preferably 0.07 mm or greater, and even more preferably,0.1 mm or greater.

Next, a slide metal piece the same as that of the actual test above, andin which the slit angles are 17° (cross slitting) was used, and as shownin FIG. 8, the relative slippage was measured. As shown in FIG. 8, theslide metal piece 10 was mounted in the large end 1 and a crank pin 15was fit into the slide metal piece 10. In addition, the mating surfaceat the left side of the ring halves 10 a and 10 b which form the slidemetal piece 10 was used as a reference position, and from this referenceposition, the ring half 10 a was moved in a clockwise direction, and atarget plate 25 which extends in the radial direction was fixed to the10°, 50°, 130°, and 170° positions, respectively. Furthermore, adistance sensor 30 which causes the detecting portion to approach thetarget plate 25, was mounted on the rod portion 3 of the large end 1. Inthis state, a load of approximately 2000 kgf was applied to the crankpin 15 and the connecting rod, and both were deformed so as to be pulledapart in the vertical direction in the figure. At the position of thedistance sensor 30 shown in FIG. 8, when relative slippage of the outerperipheral surface of the slide metal piece 10 with respect to the innerperipheral surface of the hole 2 of the large end 1 is caused, thetarget plate 25 moves away from the distance sensor 30. The amount ofmovement was then measured as relative slippage. Also, for the sake ofcomparison, a slide metal piece which was the same as that used in theactual test except that the slit angle was 0.5° and the slitting waslinear, was used and relative slippage was measured under the sameconditions as described above. The results are shown in FIG. 9.

As shown in FIG. 9, in the connecting rod in which a slide metal piecehaving a slit angle of 17° was mounted, the relative slippage was atmost, 4 μm less than that in which the slit angle of the slide metalpiece mounted was 0.50°. From this it can be seen that the presentinvention is effective in preventing rotation of the slide metal piece,and in restricting relative slippage.

As described above, in the present invention, by providing slits in acircumferential direction at a fixed angle on the inner peripheralsurface of the hole of the connecting rod, rotation and relativeslippage of the slide metal piece is restricted, and thus the effect isobtained of eliminating problems such as damage and heating up of thenail of the slide metal piece and generation of fretting and the like.

What is claimed is:
 1. An internal combustion engine connecting rodcomprising a hole in an end of the connecting rod main body, the endbeing divided into a plurality of parts which are in a circumferentialdirection with respect to the hole, and a slide member composed of apair of ring halves is disposed on an inner peripheral surface of thehole, wherein the inner peripheral surface of the hole is provided withmachining marks extending in one direction at an angle of 13 to 90° withrespect to the circumferential direction, and the slide member ismounted into the hole with a tightness defined by difference betweenouter circumferential length of the slide member and innercircumferential length the hole of no less than 0.1 mm, whereby the sliptorque necessary for causing relative rotation of the slide member andthe hole is no less than 15 kgf·m when the slide member is mounted intothe hole and a force causing relative rotation of the slide member andthe hole is applied thereto.
 2. The internal combustion engineconnecting rod of claim 1, wherein the angle of the machining marks withrespect to the circumferential direction is no more than 35°.
 3. Theinternal combustion engine connecting rod of claim 2, wherein the holehas an inner peripheral portion with a surface roughness (Ry) of 2 to 3μm.
 4. An internal combustion engine connecting rod comprising a hole inan end of the connecting rod main body, the end being divided into aplurality of parts which are in a circumferential direction with respectto the hole, and a slide member composed of a pair of ring halves isdisposed on an inner peripheral surface of the hole, wherein the innerperipheral surface of the hole is provided with machining mark extendingin one direction at an angle of 17 to 90° with respect to thecircumferential direction, and machining marks that extend in adirection crossing the one direction, and the slide member is mountedinto the hole with a tightness defined by difference between outercircumferential length of the slide member and inner circumferentiallength of the hole of no less than 0.1 mm, whereby the slip torquenecessary for causing relative rotation of the slide member and the holeis no less than 15 kgf·m when the slide member is mounted into the holeand a force causing relative rotation of the slide member and the holeis applied thereto.
 5. The internal combustion engine connecting rod ofclaim 4, wherein the angle of the machining marks with respect to thecircumferential direction is no more than 35°.
 6. The internalcombustion engine connecting rod of claim 5, wherein the hole has aninner peripheral portion with a surface roughness (Ry) of 2 to 3 μm.